Device for the measurement of intermodulation products of a receiver system

Abstract

A device to measure intermodulation products of a receiver of at least two electromagnetic signals of different frequencies comprises at least two channels for the transmission of the signals of different frequencies and one reflective reception channel connected to an apparatus for the measurement of intermodulation products. The reception channel enables the transfer of signals in a frequency band centered on the reception frequency band of the receiver. A reflective reception multiplexer/demultiplexer with directional filters provides for the interconnection of the two transmission channels of the reflective reception channel of the receiver.

What is claimed is: 
     
       1. A device for the measurement of intermodulation products of a receiver system of at least two transmitted electromagnetic signals of different frequencies said device comprising: at least two transmission channels for said transmitted electromagnetic signals, each channel enabling the transfer of one of said signals of different frequencies;   a reflective reception channel connected to an apparatus for the measurement of intermodulation products, said reception channel enabling the transfer of electromagnetic signals in a frequency band centered on the reception frequency band of said receiver;   a reflective reception multiplexer/demultiplexer with directional filters, the inputs/outputs of which are respectively connected to said first and second transmission channels, to the reflective reception channel and to said receiver system, said multiplexer/demultiplexer comprising a directional filter associated with each channel, each of said directional filters transmitting at the frequency of the electromagnetic signals transferred by the channel with which it is associated and being reflective at the frequency of the electromagnetic signals of the other channels and of the intermodulation products located outside the reception frequency band.   
     
     
       2. A device according to claim 1, wherein said directional filters are constituted by: a first hybrid coupler, the first input port of which receives the electromagnetic signal of a frequency corresponding to the frequency of the channel considered;   two identical filters enabling the transfer of electromagnetic signals in a frequency band centered on the frequency of the channel considered, each filter being connected respectively to the output port of the first hybrid coupler;   a second hybrid coupler, each input port of which is connected to the output of one of the two identical filters, and the second output port of which delivers the electromagnetic signal of a frequency corresponding to the frequency of the channel considered, and the first output port of which is connected either to a dissipative load or to the second output port of the second hybrid coupler of another directional filter, the second input port of the first hybrid coupler being connected either to a dissipative load or to the second output port of the second hybrid coupler of another directional filter.   
     
     
       3. A device according to claim 2, wherein, in order to ensure a measurement of reflective intermodulation products of said receiver system for two transmitted electromagnetic signals of different frequencies: the first and second input ports of the first hybrid coupler of the first directional filter are respectively connected to the first transmission channel and to a dissipative load, the first output port of the second hybrid coupler of said first directional filter being connected to a dissipative load;   the first and second input ports of the first hybrid coupler of the second directional filter are respectively connected to the second transmission channel and to a dissipative load, the first output port of the second hybrid coupler of the second directional filter being connected to the second output port of the second hybrid coupler of the first directional filer;   the first and second input ports of the first hybrid coupler of the third directional filter are respectively connected to the receiver system to be tested and at the second output port of the second hybrid coupler of the second directional filter, the first and second output ports of the second hybrid coupler of the third directional filter being respectively connected to the reflective reception channel and to a dissipative load.   
     
     
       4. A device according to claim 2, wherein, in order to ensure a measurement of transferred intermodulation products of said receiver system for two transmitted electromagnetic signals of different frequencies, said device further comprises a transfer reception channel and a transfer reception multiplexer/demultiplexer with directional filters. 
     
     
       5. A device according to claim 4, wherein said transfer reception multiplexer/demultiplexer with directional filters has at least one fourth directional filter which transmits in the frequency band of the transferred intermodulation product signals and is reflective at the frequency of the transferred signals and of the intermodulation products outside the transfer band. 
     
     
       6. A device according to claim 5, wherein said fourth directional filter comprises: a first hybrid coupler, the first input port of which is connected to an output of intermodulation products of the receiver system, and the second input port of which is connected to a dissipative load, the output ports of the first hybrid coupler being connected respectively to a first filter and a second filter, identical to each other, the transferred frequency band of which is centered on the transfer frequency band or frequency of the receiver system;   a second hybrid coupler, the input ports of which are respectively connected to an output of said first and second filters, and the first and second output port of which are respectively connected to a dissipative load and to said transfer reception channel.   
     
     
       7. A device according to claim 5 wherein said transfer reception multiplexer/demultiplexer with directional filters further comprises: a fifth directional filter which transmits in the frequency band corresponding to the first transmission frequency and is reflective in all the other frequency bands;   a sixth directional filter which transmits in the frequency band corresponding to the second transmission frequency and is reflective in all the other frequency bands.   
     
     
       8. A device according to claim 7, wherein said fifth directional filter of said transfer reception multiplexer/demultiplexer comprises: a first hybrid coupler, the input port of which is connected to the second input port of the first hybrid circuit of the fourth directional filter, the dissipative load being eliminated;   two identical filters, the pass-band of which is centered on the frequency band, corresponding to the first transmission frequency, respectively connected to the first and second input ports of said first hybrid coupler of said fifth directional filter;   a second hybrid coupler, the input ports of which are respectively connected to an output of each identical filter and the output ports of which are themselves respectively connected to a dissipative load; and   wherein said sixth directional filter of said transfer reception multiplexer/demultiplexer comprises: a first hybrid coupler, the first input port of which is connected to the second input port of the first hybrid coupler of said firth directional filter, and the second input port of which is connected to a dissipative load;   two identical filters, the pass-band of which is centered on the frequency band, corresponding to the second transmission frequency, respectively connected to the first and second output ports of said first hybrid coupler of said sixth directional filter; and   a second hybrid coupler, the input ports of which are respectively connected to an output of each of the two identical filers of said sixth directional filter and the output ports of which are themselves respectively connected to a dissipative load.     
     
     
       9. A device according to claim 4, wherein said transmission channels, said reflective reception channel and said transfer reception channel comprise filtering means and means to amplify the filtered signal. 
     
     
       10. A device according to claim 9, wherein said filtering means are constituted by a comb filter. 
     
     
       11. A device according to claim 1, wherein, for transmission frequencies lower than about 1000 MHz, the interconnection of the various elements is achieved by means of coaxial cables. 
     
     
       12. A device according to claim 1, wherein, for transmission frequencies higher than 1200 MHz, the interconnection of the various elements is achieved in waveguide form. 
     
     
       13. A device according to claim 4, wherein the reflective reception channel and the transfer reception channel are connected to said measuring apparatus by means of a change-over switch. 
     
     
       14. The use of a measuring device according to claim 1 to measure intermodulation products of a receiver such as a radar receiver antenna or a satellite telecommunications antenna.